Method for monitoring exhaust brake pressure of engine

Abstract

The invention discloses a method for monitoring exhaust brake pressure of an engine, relates to the technical field of exhaust brake of internal combustion engines, and solves the technical problem that the existing exhaust brake test mode cannot effectively detect exhaust brake butterfly valves of engines produced in batches to cause valve faults. The method comprises the steps that actually-measured pressure values after EGR cooling under different engine working conditions are obtained, an exhaust braking pressure calculation value is obtained through calculation according to the actually-measured pressure values after EGR cooling, and when the exhaust braking pressure calculation value is smaller than a preset exhaust braking pressure threshold value, the exhaust braking function of the engine is normal. According to the invention, efficient utilization of resources is realized, and the maintenance cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engine exhaust braking technology, and more specifically, to a method for monitoring engine exhaust braking pressure. Background Technology

[0002] Exhaust braking is an auxiliary braking method for internal combustion engine vehicles. It increases exhaust back pressure by closing a butterfly valve installed in the exhaust system, thereby reducing engine speed and achieving deceleration. However, in practical applications, due to factors such as manufacturing tolerances and assembly differences, the consistency of exhaust braking butterfly valves on different vehicles is poor, resulting in significant differences in exhaust pressure after the butterfly valve is closed, and thus varying auxiliary braking effects. Although exhaust braking testing is conducted during engine product development, mass-produced engines may be equipped with exhaust butterfly valves from different manufacturers, and even between different butterfly valve samples from the same manufacturer, there are performance consistency issues. This makes it impossible to effectively monitor the engine exhaust pressure when the exhaust butterfly valve is closed for every engine leaving the factory. When the engine exhaust pressure is too high, it may cause malfunctions such as valve spring rebound, valve re-opening, or even valve knock-out, resulting in the scrapping of the entire engine. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for monitoring engine exhaust brake pressure, which addresses the shortcomings of the existing technology and solves the technical problem that the existing exhaust brake testing method cannot effectively detect the exhaust brake butterfly valve of mass-produced engines, thus causing valve failure.

[0004] The present invention discloses a method for monitoring engine exhaust brake pressure. The method involves obtaining the measured pressure value of EGR after cooling under different engine operating conditions, calculating the exhaust brake pressure value based on the measured pressure value of EGR after cooling, and determining that the exhaust brake function of the engine is normal when the calculated exhaust brake pressure value is less than a preset exhaust brake pressure threshold.

[0005] As a further improvement, the calculation expression for the exhaust brake pressure is as follows:

[0006] ; Where P is the calculated value of exhaust brake pressure, k is the pressure coefficient, and b is the pressure deviation.

[0007] Furthermore, when the calculated exhaust brake pressure value is greater than or equal to the exhaust brake pressure threshold, an alarm is issued to alert the staff.

[0008] Furthermore, the method for setting the exhaust braking pressure threshold is as follows: The engine's real-time speed is obtained, and a standard range of engine speed is set. When the real-time speed is within the standard range of engine speed, the target exhaust brake pressure threshold is calibrated based on the real-time speed and the measured pressure value after EGR cooling. When the real-time speed is less than the minimum value of the standard range of engine speed, the difference between the minimum value of the standard range of engine speed and the real-time speed is used to obtain a first speed difference value. The first speed difference value is multiplied by a preset speed difference-exhaust brake pressure correlation coefficient to obtain a first exhaust brake pressure correction threshold. The first initial exhaust brake pressure threshold is calibrated according to the minimum value of the standard range of engine speed and the real-time speed. The first initial exhaust brake pressure threshold is added to the first exhaust brake pressure correction threshold to obtain a first exhaust brake pressure threshold. The first exhaust brake pressure threshold is used as the target exhaust brake pressure threshold. The second exhaust brake pressure threshold is calibrated based on the maximum value of the standard engine speed range and the measured pressure value after EGR cooling. When the real-time speed is greater than the maximum value of the standard engine speed range, the second exhaust brake pressure threshold is used as the target exhaust brake pressure threshold.

[0009] Furthermore, the standard speed range of the engine is 650 r / min to 2550 r / min.

[0010] Beneficial effects The advantages of this invention are: 1. This invention obtains the measured pressure value of EGR after cooling under different engine operating conditions, and calculates the exhaust brake pressure value based on the measured pressure value of EGR after cooling. When the calculated exhaust brake pressure value is less than the preset exhaust brake pressure threshold, the exhaust brake function of the engine is normal. It makes full use of the original EGR pressure sensor of the engine, avoids the cost increase caused by installing an additional dedicated exhaust pressure sensor, realizes efficient use of resources, and reduces maintenance costs.

[0011] 2. When the calculated exhaust braking pressure value is greater than or equal to the exhaust braking pressure threshold, the present invention will issue an alarm to remind the staff; it can promptly warn and detect abnormal engine exhaust pressure, effectively preventing various malfunctions (valve overshoot, valve re-opening, etc.) caused by excessive exhaust pressure, thereby ensuring the safe and reliable operation of the engine. Attached Figure Description

[0012] Figure 1 This is a flowchart of the engine exhaust brake pressure monitoring method of the present invention; Figure 2 This is a schematic diagram of the engine exhaust brake butterfly valve arrangement structure of the present invention; Figure 3This is a graph showing the changes in the measured exhaust braking pressure and the measured pressure after EGR cooling of the first engine of the same model tested in this invention within the standard engine speed range. Figure 4 This is a graph showing the changes in the measured exhaust braking pressure and the measured pressure after EGR cooling of a second engine of the same model tested in this invention within the standard engine speed range. Figure 5 This is a graph showing the changes in the measured exhaust braking pressure and the measured pressure after EGR cooling of the third engine of the same model tested in this invention within the standard engine speed range. Figure 6 This is a curve comparing the measured value of exhaust brake pressure with the calculated value of exhaust brake pressure of the first engine of the same model tested in this invention. Figure 7 This is a curve comparing the measured value and the calculated value of the exhaust brake pressure of the second engine of the same model tested in this invention. Figure 8 This is a curve comparing the measured value and the calculated value of the exhaust braking pressure of the third engine of the same model tested in this invention.

[0013] Among them: 1- Engine front exhaust system, 2- Turbocharger, 3- Turbo rear pipe, 4- Exhaust brake butterfly valve, 5- Aftertreatment system, 6- EGR intake pipe, 7- EGR cooler, 8- EGR pressure sensor, 9- EGR valve. Detailed Implementation

[0014] The present invention will be further described below with reference to embodiments, but this does not constitute any limitation on the present invention. Any limited modifications made by any person within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0015] See Figures 1-8 The present invention provides a method for monitoring engine exhaust brake pressure, wherein the method is as follows: Step 1: Select one or more representative engines as test subjects, ensuring that the engines have standard EGR pressure sensors and exhaust brake butterfly valves. EGR pressure data acquisition: Read the cooled EGR pressure value from the engine's ECU. This process requires no modification to existing hardware, ensuring the solution's economy and ease of use. It fully utilizes the engine's existing EGR pressure sensor, avoiding the increased cost of installing a dedicated exhaust pressure sensor, achieving efficient resource utilization and reducing maintenance costs.

[0016] like Figure 2As shown, the exhaust port of the engine turbocharger exhaust system 1 is connected to the turbocharger 2. The exhaust port of the engine turbocharger exhaust system 1 is connected to the EGR cooler 7 through the EGR intake pipe 6. The EGR cooler 7 is connected to the EGR valve 9. An EGR pressure sensor 8 is installed between the EGR cooler 7 and the EGR valve 9.

[0017] The exhaust port of the turbocharger 2 is connected to the engine's aftertreatment system 5 via the turbocharger 2, the turbine rear pipe 3, and the exhaust brake butterfly valve 4, which are connected in sequence.

[0018] Step 2: Design a series of bench test schemes covering different working conditions, and record the pressure value of EGR after cooling and the corresponding measured value of exhaust brake pressure under each test condition.

[0019] Step 3: Based on the collected data, statistical methods are used to analyze the correlation between the two and derive the best-fit model as the basis for subsequent monitoring.

[0020] An EGR pressure sensor is installed after the engine EGR cooler, and an exhaust brake pressure sensor is installed before the exhaust butterfly valve. Engine speed is monitored and collected synchronously. Pressure sensor data is recorded at different engine speeds. An xy-line graph is plotted with EGR pressure as the x-axis and exhaust brake pressure as the y-axis, as shown below. Figure 3 .

[0021] like Figure 3 As shown, there is a linear relationship between EGR pressure and exhaust brake pressure: y = 0.8865. x+4.0195, the pressure coefficient k=0.8865, pressure deviation b=4.0195, and the formula y=k×x+ b are stored in the engine ECU. Given the engine speed and EGR pressure data, the ECU can calculate the corresponding exhaust brake pressure using the formula. When the engine speed is not an integer, linear interpolation is used for calculation. The exhaust brake pressure data is uploaded to the terminal for real-time monitoring. The above test was repeated using two other engines of the same model; the test results are shown below. Figure 4 and 5 .

[0022] Step 4: Verify the calculation model under different driving conditions on the vehicle to further verify its accuracy.

[0023] Data proves that a linear relationship exists between EGR pressure and exhaust brake pressure. Averaging the k and b values ​​of the three sets of data yields km = 0.8920 and bm = 3.8963. Substituting these averages into the formula, we get exhaust brake pressure = 0.8920 × EGR pressure + 3.863. The exhaust brake pressure calculated using the formula from the EGR pressure of the above three sets of data, along with the measured values ​​and their deviations, are shown below. Figure 6-8 The deviation between the calculated and measured values ​​of exhaust brake pressure for the three sets of data is within ±5 kPa. Writing this formula into the ECU to calculate exhaust brake pressure in real time can meet the requirements of real-time monitoring and early warning functions for exhaust brake pressure.

[0024] Step 5: The calculation model is integrated into the ECU, enabling it to automatically perform the conversion calculation from EGR pressure to exhaust brake pressure during normal vehicle operation and feed the results back to the control system.

[0025] Obtain the measured pressure values ​​of EGR after cooling under different engine operating conditions, and calculate the exhaust brake pressure value based on the measured pressure values ​​of EGR after cooling.

[0026] Establishing a correlation: Through bench testing, a linear relationship was found between the EGR pressure measured by the EGR sensor and the exhaust brake pressure. The expression for calculating the exhaust brake pressure is as follows: ; Where P is the calculated value of exhaust brake pressure, k is the pressure coefficient, and b is the pressure deviation. These two parameters can be determined through a series of tests and stored in the ECU for real-time calculation.

[0027] Step 6: Based on the needs of actual application scenarios, set reasonable alarm thresholds and response mechanisms. For example, when the expected exhaust braking pressure exceeds 350 kPa, promptly remind the driver to take appropriate action to handle the problem and upload the data to the vehicle network so that the engine manufacturer can take targeted measures.

[0028] When the calculated exhaust brake pressure is less than the preset exhaust brake pressure threshold, the engine's exhaust brake function is normal. When the calculated exhaust brake pressure is greater than or equal to the exhaust brake pressure threshold, an alarm will be issued to alert the operator.

[0029] Real-time monitoring and alarm: During engine operation, the ECU continuously monitors and collects EGR pressure, and calculates the current exhaust brake pressure based on the above model. If the exhaust pressure exceeds the preset alarm threshold (e.g., 350 kPa), the alarm mechanism is immediately triggered to remind the driver to take appropriate measures, such as stopping the engine to check or replace the butterfly valve, to avoid potential malfunctions. This effectively prevents various malfunctions caused by excessive exhaust pressure (valve knock-off, valve re-opening, etc.), thereby ensuring the safe and reliable operation of the engine.

[0030] When the engine speed is too low (such as at idle or starting), the piston movement is slow and the exhaust flow is small. If a high exhaust back pressure is applied at this time, it is very easy for the exhaust gas to be unable to be discharged smoothly. The pressure will act backward on the engine, which may cause the exhaust valve to fail to close properly, damage the turbocharger, or even engine stall or serious mechanical damage. Therefore, this invention provides a method for dynamically setting an exhaust braking pressure threshold. The method for setting the exhaust braking pressure threshold involves obtaining the real-time engine speed and setting a standard engine speed range, such as... Figure 3-5 As shown, the standard engine speed range is 650 r / min to 2550 r / min. When the real-time engine speed is within the standard range, the target exhaust brake pressure threshold is calibrated based on the real-time engine speed and the measured pressure value after EGR cooling.

[0031] When the real-time engine speed is less than the minimum value of the standard engine speed range, the difference between the minimum value of the standard engine speed range and the real-time engine speed is used to obtain a first speed difference value. This first speed difference value is then multiplied by a preset speed difference-exhaust brake pressure correlation coefficient to obtain a first exhaust brake pressure correction threshold. Based on the minimum value of the standard engine speed range and the real-time engine speed, a first initial exhaust brake pressure threshold is calibrated. This first initial exhaust brake pressure threshold is then added to the first exhaust brake pressure correction threshold to obtain a first exhaust brake pressure threshold. This first exhaust brake pressure threshold is used as the target exhaust brake pressure threshold. In this embodiment, the exhaust brake pressure correlation coefficient is 0.52.

[0032] The second exhaust braking pressure threshold is calibrated based on the maximum value of the standard engine speed range and the measured pressure value after EGR cooling. When the real-time engine speed exceeds the maximum value of the standard engine speed range, the second exhaust braking pressure threshold is used as the target exhaust braking pressure threshold. This method of setting the exhaust braking pressure threshold can fundamentally avoid dangerous high back pressure caused by false triggering or high demand at low speeds, providing the most direct protection for the engine. It ensures precise matching between the establishment and release of braking force and engine operating conditions, avoiding sudden intervention or disappearance of braking force, thereby reducing vehicle jerking and improving control quality when descending long slopes; achieving a balance between control precision and safety redundancy.

[0033] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention, and these will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A method for monitoring engine exhaust brake pressure, characterized in that, The method involves obtaining the measured pressure value of EGR after cooling under different engine operating conditions, calculating the exhaust brake pressure value based on the measured pressure value of EGR after cooling, and determining that the exhaust brake function of the engine is normal when the calculated exhaust brake pressure value is less than a preset exhaust brake pressure threshold.

2. The method for monitoring engine exhaust brake pressure according to claim 1, characterized in that, The calculation expression for the exhaust brake pressure is as follows: ； Where P is the calculated value of exhaust brake pressure, k is the pressure coefficient, and b is the pressure deviation.

3. The method for monitoring engine exhaust brake pressure according to claim 1, characterized in that, When the calculated exhaust brake pressure value is greater than or equal to the exhaust brake pressure threshold, an alarm will be issued to alert the staff.

4. The method for monitoring engine exhaust brake pressure according to claim 1, characterized in that, The method for setting the exhaust brake pressure threshold is as follows: The engine's real-time speed is obtained, and a standard range of engine speed is set. When the real-time speed is within the standard range of engine speed, the target exhaust brake pressure threshold is calibrated based on the real-time speed and the measured pressure value after EGR cooling. When the real-time speed is less than the minimum value of the standard range of engine speed, the difference between the minimum value of the standard range of engine speed and the real-time speed is used to obtain a first speed difference value. The first speed difference value is multiplied by a preset speed difference-exhaust brake pressure correlation coefficient to obtain a first exhaust brake pressure correction threshold. The first initial exhaust brake pressure threshold is calibrated according to the minimum value of the standard range of engine speed and the real-time speed. The first initial exhaust brake pressure threshold is added to the first exhaust brake pressure correction threshold to obtain a first exhaust brake pressure threshold. The first exhaust brake pressure threshold is used as the target exhaust brake pressure threshold. The second exhaust brake pressure threshold is calibrated based on the maximum value of the standard engine speed range and the measured pressure value after EGR cooling. When the real-time speed is greater than the maximum value of the standard engine speed range, the second exhaust brake pressure threshold is used as the target exhaust brake pressure threshold.

5. The method for monitoring engine exhaust brake pressure according to claim 4, characterized in that, The standard engine speed range is 650 r / min to 2550 r / min.

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